Lawn Grass as A Sustainable Adsorbent for Nickel(II) Removal
DOI: https://doi.org/10.55373/mjchem.v24i2.29
Keywords: Adsorbent; lawn grass; nickel(II); sustainable; waste to resource
Abstract
Lawn grass is a waste that has the potential to be converted into an adsorbent to remove nickel(II) from aqueous solution. The methodology includes preparation of the adsorbent, performance of nickel(II) adsorption, evaluation of existing models and characterization of absorbent by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX). The results showed the optimum adsorbent amount, initial pH and time were 0.35 g, 5.62 + 0.38 and 30 minutes, respectively. Inductively coupled plasma - optical emission spectroscopy (ICP-OES) results suggested an ion exchange mechanism through a displacement of alkaline and alkaline earth metal ions by nickel(II) ions. The results were a better fit to the Langmuir isotherm than Freundlich, with a maximum uptake of 42.02 mg/g. The calculated Langmuir maximum uptake value was comparable to other adsorbents. The adsorption performance corresponded excellently with the pseudo-second-order kinetic model compared to the pseudo-first-order kinetic model. These findings indicated that adsorption of nickel(II) using lawn grass involved a homogeneous monolayer surface, with chemisorption as the rate-limiting step. Thermodynamic evaluation revealed that the adsorption process of nickel(II) by lawn grass is non- spontaneous with weak reversible bonding and endothermic reaction. SEM results showed that the irregular and highly porous surface of lawn grass became smooth after the adsorption of nickel(II). The EDX results supported the ICP analysis which suggested an ion exchange mechanism was involved.